title: Inhibition of inositol 1,4,5-trisphosphate-induced Ca2+ release by cAMP-dependent protein kinase in a living cell.
abstract: Interaction of intracellular free calcium ([Ca2+]i) and cAMP signaling mechanisms was examined in intact single megakaryocytes by using a combination of single-cell fluorescence microscopy to measure [Ca2+]i and flash photolysis of caged Ca2+, inositol 1,4, 5-trisphosphate (IP3), or cAMP to elevate rapidly the concentration of these compounds inside the cell. Photolysis of caged IP3 stimulated Ca2+ release from an IP3-sensitive store. The cAMP-elevating agent carbacyclin inhibited this IP3-induced rise in [Ca2+]i but did not affect the rate of Ca2+ removal from the cytoplasm after photolysis of caged Ca2+. Photolysis of caged cAMP during ADP-induced [Ca2+]i oscillations caused the [Ca2+]i oscillation to transiently cease without affecting the rate of Ca2+ uptake and/or extrusion. We conclude that the principal mechanism of cAMP-dependent inhibition of Ca2+ mobilization in megakaryocytes appears to be by inhibition of IP3-induced Ca2+ release and not by stimulation of Ca2+ removal from the cytoplasm. Two inhibitors of cAMP-dependent protein kinase, a specific peptide inhibitor of the catalytic subunit of cAMP protein kinase and KT5720, blocked the inhibitory effect of carbacyclin, indicating that the inhibition of IP3-induced Ca2+-release by carbacyclin is mediated by cAMP-dependent protein kinase.
authors.affiliation: Department of Physiology, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3505, USA.
authors.forename: S
authors.initials: S
authors.lastname: Tertyshnikova
authors.forename: A
authors.initials: A
authors.lastname: Fein
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002227:Carbazoles; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011464:Epoprostenol / Q000031:analogs & derivatives / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D008533:Megakaryocytes / Q000378:metabolism*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D010975:Platelet Aggregation Inhibitors; D011758:Pyrroles; C057416:KT 5720; D000244:Adenosine Diphosphate; C026678:carboprostacyclin; D015544:Inositol 1,4,5-Trisphosphate; D011464:Epoprostenol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002118:Calcium